TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  3662
SUBJECT: GRB 050721: early afterglow light curve
DATE:    05/07/22 23:00:24 GMT
FROM:    Daniele Malesani at SISSA-ISAS,Trieste,Italy  <malesani@sissa.it>

V. Testa, L.A. Antonelli (INAF/OAR), D. Malesani (SISSA), S. Covino, P. 
D'Avanzo, G. Tagliaferri (INAF/OABr), G. Chincarini (Univ. 
Milano-Bicocca), G.L. Israel, S. Piranomonte, L. Stella (INAF/OAR), 
report on behalf of the MISTICI collaboration:

We analyzed the full dataset of the early light curve of the afterglow 
of GRB 050721 (Antonelli et al., GCN 3654; Torii, GCN 3655; Covino et 
al., GCN 3657), obtained with the ESO VLT in rapid response mode.

The observation, performed in the R band, started 25 min after the GRB 
and lasted for 107 minutes (till the object set). It was composed by 
several short (30 s), repeated exposures. The light curve is well 
described by a single power law, with decay index 1.20 +- 0.01. The 
decay is smooth, without any significant rebrightening or deep.

We acknowledge the excellent support provided by the ESO staff in 
performing the observations.

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